The invention relates to web transport, and more particularly to web transport in heat transfer decorators.
One type of heat transfer decorator uses a carrier web to transport labels past a preheater, where each is heated, to a decorating site, where each label is pressed against the surface of an article to transfer it to the article.
Illustrative U.S. patents include: U.S. Pat. Nos. 2,981,432; 3,064,714; 3,079,979; 3,193,211; 3,208,897; 3,231,448; Re. 26,226; and 3,483,063.
In designing a suitable web transport or label carrier for decorators, it is desirable that the motion of the web at the decorating site match that of the article. The labels must also be properly registered with the article surface during decoration. Additionally the web must be maintained at a suitable tension throughout its length.
As illustrated for example in U.S. Pat. No. 3,079,979, FIG. 2, a label carrier employed can have a label bearing portion with periodically spaced labels, and a margin for evenly spaced sprocket holes. The label carrier web is fed from an unwind roll through a series of "dancer" and "idler" rolls to a metering roll, and thence past a preheater and through the decorating site, and further dancer and idler rolls to a rewind roll. The metering roll includes a peripheral sprocket which engages the sprocket holes of the web to register the speed of the web and control the average web speed. Shuttle rolls are mounted astride the label transfer site on a reciprocating label shuttle, which accelerates the local web speed when extending, and decelerates the web speed when retracting. This permits a closer spacing of labels on the carrier web. The web is pulled through the various transport stations by the takeup reel, which rotates at a surface speed matching that of the metering roll. Brake and clutch assemblies at the unwind and takeup reels respectively, together with dancer rolls, provide torque adjustments for the reels to regulate web tension.
This prior art web transport system has proven quite satisfactory in operation, but encounters certain disadvantages attributable to the use of non-circular containers being used with a round type turret. The system cannot properly accelerate the web or the container surface during transfer of the label to non-circular containers. Oval shaped containers for example are frequently used to package consumer products. Such oval shaped containers, using heat transfer decorators with round type turrets, rotate at a constant angular velocity. As a result they suffer distortion of the labels upon transfer because the velocity of the label receptive surface does not match that of the carrier web at all times during the transfer interval.
Accordingly, it is an object of the invention to provide an improved web transport system, particularly for heat transfer decorators. A related object is to achieve a web transport which regulates web speed at the decorating site to reduce distortion in the labelling of irregularly shaped containers.